Structural, elastic, electronic, phonon, dielectric and optical properties of Bi₃TeBO₉ from first-principles calculations

The energy band structure, electronic density of states, elastic constants, phonon spectrum, dielectric and optical properties of Bi₃TeBO₉ (BTBO) were studied by means of the first-principles calculations. The obtained structural parameters from PBEsol functional method are in good agreement with the experiment values. From the elastic constants, the bulk modulus (B), shear modulus (G), Young's modulus (E), Poisson's ratio (ν and ν_ij), ratio of B/G and C₁₂-C₄₄ have been obtained. The BTBO is found to be ductile. The energy band structure and DOS indicate that the nonlinear optical (NLO) properties are dominated by the electron jumping from the top of the valence bands to the bottom of the conduction bands. The phonon and dielectric properties of BTBO were calculated, indicating that the BTBO is dynamically stable and has relatively high dielectric constant. Moreover, the optical properties such as dielectric function ε(ω), refractive index n(ω), extinction coefficientk(ω), absorption coefficient α(ω), optical reflectivityR(ω) and energy-loss function L(ω) were calculated and analyzed.